1. Field of the Invention
Embodiments of the present invention relate generally to a vision system, a method for inspecting a processing system and a method for determining the position of an object within a processing system.
2. Background of the Invention
The use of robots in automated processing systems has become increasingly popular. Robots can often perform repeated tasks with the precision and efficiency generally not achievable through the use of human labor. Moreover, robots can be used in locations where the proximity to moving components or sensitive environments makes the use of human labor in such locations undesirable.
This is particularly important in semiconductor processing systems where misplaced or out-of-position substrates result in costly damage or/and unscheduled system maintenance. Misaligned substrates are often damaged, damage other substrates or equipment, or are poorly processed due to misalignment and may be discarded. For example, a substrate disposed on an end effector of a robot of a semiconductor processing system may come into contact with a misaligned substrate during movement of the substrate that is secured to the robot. If the substrates contact one another, one or both of the substrates may become damaged. Moreover, if one or both of the substrates become dislodged, the system must be shut down for the removal of the substrate before further processing can occur. If retrieval of the dislodged substrate requires accessing interior portions of the system operating under vacuum, hours of production time will be lost for decontamination and reestablishment of a vacuum environment within the affected chambers.
In order to ensure precise positioning of substrates moved by the robot, reference points or coordinates for a desired or predetermined position of the robot's end effector is typically entered into a memory of a robot controller as part of a calibration procedure. Acquiring the reference coordinates generally involves jogging the end effector to the predetermined position, typically through a manual or an automated sequence. Arrival of the robot's end effector at the predetermined position may be confirmed by manually observing the end effector position, or by having the end effector (or other component of the robot) trigger a sensor, such as a limit switch. This sequence is typically repeated until all the reference coordinates for each critical position within the robot's range of motion throughout the system has been established (i.e., entered into the robot's or robot controller's memory). Once the reference coordinates have been established, the robot can move the end effector with precision and accuracy into critical positions by returning to the reference coordinates.
In many semiconductor processing systems, jogging of the robot's end effector and the confirmation of the end effector's arrival at the reference coordinate is done manually. An operator must observe the location of the end effector relative to an object or target within the processing system to visually estimate the position of the end effector. In order to adequately view the end effector when performing this task, the processing system is typically opened to the surrounding environmental. This undesirably places the operator in a position exposed to the range of motion of the robot where personal injury or system damage may occur. Thus, to prevent possible injury to the operator, the processing system is normally shut down so that the robot does not inadvertently make contact with the operator, possibly damaging product, tooling or the operator. As the system is exposed to the surrounding environment, decontamination procedures must be performed prior to processing. Moreover, lengthy pump-downs must be performed to return the system to operation pressures. During periods when the system is shut down, no wafers are processed and valuable production time is lost. This all results in undesirable loss of production capacity, with further capacity lost whenever recalibration is needed.
Therefore, a need exists for an improved calibration and method for determining the position of an object.